The present invention relates to a laser diode device which includes semiconductor layers made of a nitride Group III-V compound semiconductor containing at least one of aluminum (Al), gallium (Ga), and indium (In) among Group 3B elements and nitrogen (N) among Group 5B elements (hereinafter referred to as “AlGaInN compound semiconductor”), and is capable of providing high output of 200 mW or more in the blue wavelength region.
It is considered that an AlGaInN compound semiconductor is the almost only material capable of providing emission in the range from 350 nm to 600 nm, and capable of realizing a high quality laser diode particularly in the blue wavelength range (from 400 nm to 500 nm). A narrow-stripe type high density optical disc laser realizing single transverse mode by using the AlGaInN material has been already in practical use, and has shown high reliability (for example, refer to Japanese Unexamined Patent Application Publication No. 2002-299765).
However, when attempt is made to realize a so-called broad area type laser in which the width of the light emitting region is widened in order to obtain higher output by the AlGaInN material, the guideline that the width of the light emitting region shall be more widened and the resonator length shall be lengthened for obtaining high output, which is effective when using the traditional AlGaAs material and the traditional AlGaInP material, is not effective. For example, in order to put a laser diode with 1 watt level to practical use, a structure in which the width of the light emitting region is about 50 μm and the resonator length is about 1000 μm is often utilized. However, when such a structure is applied to the AlGaInN material, the characteristics are significantly deteriorated, and it is difficult to obtain desired high output.
Therefore, in the past, a method to obtain high output by arraying a plurality of lasers with relatively narrowed width of the light emitting region has been used. Though the method is effective, there is a disadvantage that the method is not readily utilized because of complication of manufacturing steps, lowering of process yield, necessity of precise alignment with a micro lens array or the like in mounting and the like.
Blue laser diodes with high output are highly promising in the field such as microfabrication, display, and health care. Realization of high output blue lasers as stable as traditional infra-red laser diodes or red laser diodes has been strongly aspired. However, in the past, no effective guideline for obtaining blue laser diodes with high output, that is, blue laser diodes with broad area has been established.